If you have a car, you’ve probably changed a flat tire at least once in your life, or have had someone change it for you. If you’re into making your car look good, the first things you change are usually the car’s wheels and tires, raising the diameter of your wheels while lowering the profile of your tires. Whether you still have your stock wheels, or you’ve decided to go aftermarket, your lug nuts are a very important part of your running gear.
Lug nuts? Do you know it? It’s the nut that holds your wheel to the hub and axle of your automobile, SUV, or any other vehicle that uses tires. However, the term “lug nut” is slowly being replaced by the phrase “wheel fastener” in the automotive industry. This is because some European makes like Mercedes Benz, BMW, Porsche, Audi, and Volkswagen use the configuration called a “bolted joint”. This uses lug bolts or wheel bolts instead of nuts. The lug bolts screw into a threaded or “tapped” hole in the vehicle’s hub, brake drum, or brake disc.
There are different kinds of lug nuts/wheel fasteners. These designs are based on the wheels fasteners’ “seat” styles, which refer to the contact area between the base of the fastener’s head and the wheel’s fastener pocket. While there are some variations that exist, there are three basic seat styles. The two most common designs for lug nuts are the rounded or conical lug nuts, and the radiused, or “ball” style. The other, less common design is the flat washer
The conical lug nut features a tapering, conical seat area, making a symmetrical, sloping edge. This type of tapering edge, called a “chamfered” edge, is most commonly found with a sixty-degree angle. However, some light pickup trucks, sport-utility vehicles, and minivans use a ninety-degree angle. This angle indicates the degree of separation between the two walls (the walls of the nut and the walls of the fastener pocket) and not the true vertical of the wheel fastener.
There are some lug nuts that have radiused, or hemispherically shaped seats, called “ball” or “rounded” seats. As the name implies, the seat is somewhat shaped like half a ball. This nestles into a ball-shaped pocket in the hub or brake drum/brake disc. Most European marques make use of the radius seat style, though usually in bolt applications.
Commonly called “mag” style, the flat washer-type wheel fastener has a flat bottom. This is only used on wheels that have a flat contact surface area, as the stamped steel wheels on small economy cars and commercial vehicles, as well as inexpensive cast alloy wheels. The word “mag” does not actually pertain to the shape or the seat. Rather, it’s just a carryover from the 1970s performance scene when race or high-performance wheels were cast magnesium. These wheels were made with a flat seat because it was easier to make just a round hole than a tapered or ball-shaped seat in the hub’s center area. Also, when using mag-style wheel fasteners, always use the washers that come with it!
One important thing you should always remember about wheel fastener is that you absolutely cannot mix seat styles! A wheel fastener with a tapered or conical seat will never fit a wheel with a radiused seat or pocket, and vice versa. The same goes for flat washer type fasteners. The seat profile of the wheel dictates the kind of wheel fastener you should use.
Using the incorrect style will definitely result in the lug nuts coming loose, and will lead to wheel damage at the very least. A potential tragedy because of the vehicle losing control when the wheel becomes loose or separates from the vehicle can be avoided entirely as long as you use the correct combination of wheels and fasteners.
One can never overemphasize this rule because the lug nuts are the only things connecting the wheels to the vehicle. Without proper fastening, you’ll find that you’re on your way to an accident.
Unfortunately, there is no way of finding out the dimensions or fitment of wheel fasteners without having to physically attempt to fit the wheel to the hub. The person who has actual physical access to the wheel and vehicle is the only one who can determine the correct fit.
To ensure that your wheels fit the hub perfectly you have to identify the following aspects of your wheel fasteners: seat type (which we discussed in the previous section), thread size, thread pitch, and length and dimensions of the stud. The color and finish of the fastener may also be important in order to match it to the wheel color. While different vehicles have different numbers of bolts on their hubs (cars and other light vehicles have 4 or 5 bolts per hub while larger vehicles such as full-size pickups, vans, and commercial vehicles have 6 or 8), this is actually not a very important factor in determining thread sizes.
Perhaps the most important of these characteristics are the thread sizing and thread pitch. Thread size refers to the diameter of the stud it will accept, while thread pitch is the number of threads per measure. When using inch format, a 1/2x20x1 wheel fastener will have a half-inch diameter (the size of the stud it will accept), 20 threads per inch, and 1 inch of internal thread engagement (the maximum depth the stud can go into the nut).
If the lug nuts are metric, the diameter is represented in millimeters. A 14x1.5x70 nut will have a 14-millimeter diameter, 1.5 threads per millimeter, and 70 millimeters of thread engagement.
A simple way to find out if the wheel fastener fits the stud perfectly is to tighten the nut by hand. If the nut can be tightened freely, then it is highly likely that the wheel fastener is of the same size as the stud. It’s much better, though, to identify the thread diameter, pitch, and length of the lug nut. You can do this using three tools: a combination of blot/nut sizing card, and two thread pitch gauges (metric and Imperial). With these tools, you can avoid playing a guessing game and be able to get your lug nuts' correct size.
One very important thing you should always remember: never oil or lubricate the threads on the lug nut or stud! Oiling or lubricating the threads can cause you to overtorque (tighten too much) the fasteners. This will cause the studs or bolts to stretch, making them liable to snap when too much load is being experienced by the wheels.
Before attaching the lug nuts, though, it is a good idea to dab some anti-seize paste on the stud. Using a torque wrench, tighten the lug nuts to factory specifications.
Anti-theft lug nuts or locking nuts are available as aftermarket accessories, although some premium brands have these as standard equipment for their vehicles. As the name implies, these prevent the theft of your vehicle’s wheels. They are actually a set of special lug nuts and a socket key. The lug nuts have a specific pattern that only the key that is part of the set can be used to remove them.
Some car owners want their vehicles to look unique. Like what was discussed in the first part of this article, most owners replace their stock wheels with aftermarket ones. A set of standard steel lug nuts usually come with the wheels. However, titanium or aluminum lug nuts are also available, and come in different anodized colors. The most common colors are black, red, gold, and blue.
Do you need new lug nuts for new rims?
While it is not that crucial to change lug nuts just because your car has new rims, it would be a good idea to change them, if only because they look good. Aftermarket lug nuts, especially the anodized aluminum type, come in different colors you can use to match the body color of your vehicle or to provide a contrast to it.
What are lug nuts made of?
Lug nuts are usually made of chrome-plated steel. However, titanium or aluminum lug nuts are available for racing applications due to their lighter weight.
Can I drive my car with only 4 lug nuts?
If your vehicle has wheel assemblies that use a five-bolt configuration, you can use only four fasteners per wheel, under emergency conditions. You should replace the missing lug nuts as soon as possible to avoid the wheels from experiencing excessive loads, thus leading to an accident.
Can you over tighten wheel nuts?
Yes, you can. This usually happens when you oil or lubricate the threads of the nut or stud.
What size socket are lug nuts?
The most common socket sizes for wheel fasteners are 13/16, 7/8, ¾, and 15/16 inch for SAE-spec tools, and 17mm and 19mm for metric tools.